The invention relates to a Hookes universal joint. The joint has two joint yokes each with two yoke arms which extend from a hub. Through-bores on each arm are arranged transversely relative to the rotational axis of the joint yokes. A supporting member with radial outer and inner portions with bores corresponding to the through-bores accommodates the yoke arms. Bearing pins are passed through the yoke arm bores and the associated supporting member bores.
German Patent No. 2,809,665 discloses a Hookes universal joint with a supporting member in the form of a ring. The ring includes four axial, circumferentially distributed apertures, with radial bores passing therethrough. The ends of the yoke arms are inserted into the apertures and secured in the rings by pins. The pins pass through bores in the supporting member and in the yoke arms. The disadvantage of this design is that the annular shape with the apertures limits the possible angle of articulation.
Another Hookes universal joint having a bearing with a single-shear connection is illustrated in German Patent DE 30 17 314 C2. The joint includes a supporting member with plate-shaped legs. The disadvantage of this design is a low torque transmitting capacity because the support with a single-shear connection may lead to edge pressure in the region of the bearings. In order to increase the torque transmitting capacity, dimensional increases are essential. Furthermore, the use of friction bearings is restricted.
It is the object of the invention to provide a Hookes universal joint which, in spite of its simple design and being made of plate metal parts for example, is capable of transmitting a higher torque than prior Hookes universal joints, without requiring any extra space.
In accordance with the invention, the objective is achieved by providing a support member positioned radially between and arranged opposite the free ends of the yoke arms. The support member has a central member with at least one radial web connecting the radially outer legs which, with an extended joint, extend parallel to the rotational axis of the joint.
The advantage of such a design is a double-shear connection. The torque transmitting capacity, as compared to prior art joints, can be increased without providing any extra space, while nevertheless achieving a larger articulation angle. Furthermore, the edge pressure is avoided, advantageously, affecting the bearing conditions. Such a measure also permits the use of friction bearings. In addition, the joint may be produced in a cost-effective way by using stamped plate-metal parts. A particularly advantageous range of application for such Hooks universal joints refers to driveshafts for driving agricultural machinery.
A particularly advantageous method of producing the supporting member is achieved if the supporting member consists of two identical supporting member parts. Each part includes a central portion, two diametrically opposed first inner legs, coupling with the yoke arms of one joint yoke and, so as to be rectangularly circumferentially offset thereto, two diametrically opposed second outer legs coupling with the yoke arms of the other joint yoke. If the two supporting member parts are assembled so as to be circumferentially offset relative to each other and point in opposite directions, the legs of each are connected to the central portion via a web.
The two supporting member parts may be formed from plate-metal and connected to each other so as to achieve a form-fitting or material-locking connection. Alternatively, it is proposed that the central portion of the supporting member should be designed to be solid, with the webs and outer legs being formed onto said central portion.
According to a further embodiment of the invention, a bearing bushing is inserted between the yoke arm bore and the bearing pin. The one end face of the bearing bushing may be supported on the inner face of the support member radially outer leg and the other end face on the outer face of the support member radial inner leg. The bearing bushings preferably contain a needle bearing.
Such a design is suitable for centering the joint yokes relative to each other via the bearing bushings. By suitably dimensioning the distances and selecting the bearing bushings in different lengths, it is possible to provide easy assembly conditions.
According to a further embodiment of the invention, it is proposed that between the two supporting member parts there should be formed a cavity for accommodating a central member. The central member is provided with bores corresponding to the yoke arm through-bores to receive the bearing pins. Also, the central member includes transverse bores for introducing pegs to lock the bearing pin in the central member. The transverse bores intersect the bearing pin bores tangentially in the region of the pin grooves which are engaged by the pegs.
The central member accommodates and centers the yoke arm bearing pins. The bearing pins are locked by pegs which are inserted into transverse bores to engage the pin grooves while permitting easy assembly and dismantling conditions.
The bearing pins are lubricated by grease which, via lubricating fittings, is pressed into a grease chamber formed by a cavity in the central member. The cavity is open towards the bores of the bearing pins.
In a further embodiment of the invention, between the two supporting member parts, a cavity is formed constituting a grease chamber. The cavity is formed by a resilient and corresponding part. The central portion of the supporting member includes central bores to center the formed parts in the central portion.
The two formed parts are arranged in the cavity of the central portion. The two formed parts form a cavity which is also intended to be used as a grease chamber for lubricating the joint. The first formed part is a truncated one which is closed at the upper tapered end. The cone includes a centrally centered outwardly directed bead. The outer face of the truncated cone includes at least one bore to enable the grease to pass from the grease chamber to the bearings. The second formed part consists of a square central face with four arms arranged to extend crosswise. Each arm is formed so as to be articulated twice and whose outer faces extend rectangularly relative to the rotational axis. The head face of the arms is provided with a groove enclosing the bearing pin at least partially in a form-fitting way. The central face also comprises a bead which is arranged centrally in the direction opposite to the articulated arms. The bead of the first and second formed part serves to center and hold the two formed parts in the two opposed supporting member parts which, for this purpose, are provided with a bore. The bearing pins in the joint yokes are secured by the grooves in the head faces of the arms of the second formed part which is held in position by the first formed part. This ensures easy assembly conditions for the Hookes universal joint. Dismantling is facilitated by exerting pressure on the first or second formed part through the central aperture in the supporting member by an auxiliary tool such as a nail or screw driver.
From the following detailed description taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.